Both studies show US Senators Lamar Alexander and Bob Corker were more willing to buck the party line: among 45 Republican senators, Alexander and Corker ranked among the least conservative. Both made CQ Roll Call’s list of Republicans most likely to vote against their party.

CQ Roll Call showed Corker voting with President Obama 50.9% of the time last year, putting him on the list of GOP senators most likely to support the president’s positions.